This invention relates to a method for forming a diffusion-controllable coating on a medical device. Such diffusion-controllable coatings may prevent and/or control out-diffusion or out-flow or release of guest materials from a medical device. In addition, this invention relates to a medical device having a diffusion-controllable coating.
Ophthalmic lenses have been used for providing an individual with improved visual acuity or visual and/or cosmetic benefits. Recently, it has been proposed that ophthalmic lenses can provide other benefits. For example, ophthalmic lenses can be used as ocular sensors for non-invasive or minimally invasive monitoring of glucose, as disclosed by March in PCT International Publication WO 01/13783. Such ocular sensors for glucose can be used to conveniently, non-invasively and frequently monitor blood glucose levels by determining glucose levels in an ocular fluid, such as tears, aqueous humor, or interstitial fluid, based on the correlation between the blood glucose concentration and the ocular glucose concentration, and whereby to achieve the tight control of blood glucose levels by managing food intake and the dosage and timing of insulin injection. Ocular glucose sensors disclosed by March in PCT International Publication WO 01/13783 can be one potentially useful non-invasive technology.
In order to fully explore the full potential of the ocular glucose sensing technology, there is an issue needed to be addressed. The issue is the out-diffusion of guest materials, such as the fluorescently labeled glucose receptor and/or the fluorescently labeled glucose competitor, from ophthalmic lenses. Such out diffusion may affect the precision and reproducibility of the ocular glucose sensing technology. Therefore, there is a need for a method of forming on an ophthalmic lenses a diffusion-controllable coating capable of controlling out-diffusion or out-flow of guest materials from the ophthalmic lens.
Furthermore, ophthalmic lenses may be served as a device for controlled delivery of therapeutic agents, besides vision corrections. For example, contact lenses may be used as a carrier for drugs to treat eye diseases, e.g., dry eye syndrome. Therefore, there is also a need for a method for forming on an ophthalmic lenses a diffusion-controllable coating capable of controlling release of drugs (guest materials) for treating eye diseases.
In addition, the manufacturing of ophthalmic lenses comprises a lengthy and costly extraction process where unpolymerized materials, such as monomers and macromers in the polymerizable composition for making ophthalmic lenses, are extracted from lenses. It is preferable that such extraction process can be eliminated from the manufacturing of ophthalmic lenses. Therefore, there is a further need for a diffusion-controllable coating capable of preventing unpolymerized raw materials (guest materials) from leaching out of the core of ophthalmic lenses.
One object of this invention is to solve the above problems by using a layer-by-layer coating process to form a diffusion-controllable coating on the surface of medical device, preferably ophthalmic lenses, more preferably contact lenses. Such coating may prevent guest materials from leaching out of the core of ophthalmic lenses or control release of therapeutic agents associated with or entrapped in the medical devices into the eye.
Another object of this invention is to produce medical devices, preferably ophthalmic lenses, more preferably contact lenses, having a diffusion-controllable coating which may prevent guest materials from leaching out of the core of ophthalmic lenses or control release of therapeutic agents associated with or entrapped in the medical devices into the eye.
This invention is partly based on discoveries that the out-diffusion of guest materials from ophthalmic lenses can be prevented by a diffusion controllable coating on ophthalmic lenses. The diffusion-controllable coating is formed on ophthalmic lenses by using a cost-effective coating process, such as a layer-by-layer (LbL) coating process.
This invention also is partly based on unexpected discoveries that the properties of LbL coating can be manipulated by changing the composition of a releasing and storage medium. Using different releasing and storage media, for example, water or phosphate buffer (PBS), the coating properties (permeability, wettability, thickness, composition, etc.) can be controlled. When using water as releasing and storage medium, LbL coatings on lenses appear to be dense/compact and have lower permeability. When using PBS as releasing and storage medium, LbL coatings on lenses appear to be more loose/fluffy and have higher permeability. Based on contact angle, LbL coatings on lenses are more wettable when using water as releasing and storage medium than when using PBS as releasing and storage medium. It has been also found that the thickness of LbL coatings on silicon wafer may depend upon the composition of a releasing and storage medium. These findings will allow us to tailor coatings with desired properties on any medical device, which will have many applications such as controlled release of different moieties (drug, nutrients, lubricants, etc), and control of out-diffusion of low or high molecular weight moieties, etc.
One aspect of the invention relates to a method for forming on a medical device, preferably an ophthalmic lens, a diffusion-controllable coating capable of controlling the out-diffusion or release of guest materials from the medical device. The method of the invention comprises: (1) applying one layer of clay and optionally one or more layers of polyionic materials onto the medical device; or (2) applying alternatively a layer of a first polyionic material and a layer of a second polyionic material having charges opposite of the charges of the first polyionic material onto the medical device and releasing the coated medical device into a releasing medium having a composition capable of imparting a desired permeability to the diffusion-controllable coating on the medical device.
Another aspect of the invention is a medical device having a diffusion-controllable coating which is capable of controlling the out-diffusion or release of guest materials from the medical device, wherein the diffusion-controllable coating is produced by: (1) applying on the medical device one layer of clay and optionally one or more layers of polyionic materials; or (2) applying alternatively a layer of a first polyionic material and a layer of a second polyionic material having charges opposite of the charges of the first polyionic material onto the medical device and releasing the coated medical device into a releasing medium having a composition capable of imparting a desired permeability to the diffusion-controllable coating on the medical device.
A further aspect of the invention is a method for manufacturing ophthalmic lenses without an extraction process, the method comprising: (1) producing ophthalmic lenses by molding in molds and/or by lathing and (2) forming a diffusion-controllable coating on each of the ophthalmic lenses produced in step (1) by a) applying thereon one layer of clay and optionally one or more layers of polyionic materials, or b) applying alternatively a layer of a first polyionic material and a layer of a second polyionic material having charges opposite of the charges of the first polyionic material onto the medical device and releasing the coated medical device into a releasing medium having a composition capable of imparting a desired permeability to the diffusion-controllable coating on the medical device.
The present invention provides the foregoing and other features, and the advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying figures. The detailed description and figures are merely illustrative of the invention and do not limit the scope of the invention, which is defined by the appended claims and equivalents thereof.